tools/perf/util/config.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * config.c
   4  *
   5  * Helper functions for parsing config items.
   6  * Originally copied from GIT source.
   7  *
   8  * Copyright (C) Linus Torvalds, 2005
   9  * Copyright (C) Johannes Schindelin, 2005
  10  *
  11  */
  12 #include <errno.h>
  13 #include <sys/param.h>
  14 #include "cache.h"
  15 #include "callchain.h"
  16 #include <subcmd/exec-cmd.h>
  17 #include "util/event.h"  /* proc_map_timeout */
  18 #include "util/hist.h"  /* perf_hist_config */
  19 #include "util/llvm-utils.h"   /* perf_llvm_config */
  20 #include "util/stat.h"  /* perf_stat__set_big_num */
  21 #include "build-id.h"
  22 #include "debug.h"
  23 #include "config.h"
  24 #include <sys/types.h>
  25 #include <sys/stat.h>
  26 #include <stdlib.h>
  27 #include <unistd.h>
  28 #include <linux/string.h>
  29 #include <linux/zalloc.h>
  30 #include <linux/ctype.h>
  31
  32 #define MAXNAME (256)
  33
  34 #define DEBUG_CACHE_DIR ".debug"
  35
  36
  37 char buildid_dir[MAXPATHLEN]; /* root dir for buildid, binary cache */
  38
  39 static FILE *config_file;
  40 static const char *config_file_name;
  41 static int config_linenr;
  42 static int config_file_eof;
  43 static struct perf_config_set *config_set;
  44
  45 const char *config_exclusive_filename;
  46
  47 static int get_next_char(void)
  48 {
  49         int c;
  50         FILE *f;
  51
  52         c = '\n';
  53         if ((f = config_file) != NULL) {
  54                 c = fgetc(f);
  55                 if (c == '\r') {
  56                         /* DOS like systems */
  57                         c = fgetc(f);
  58                         if (c != '\n') {
  59                                 ungetc(c, f);
  60                                 c = '\r';
  61                         }
  62                 }
  63                 if (c == '\n')
  64                         config_linenr++;
  65                 if (c == EOF) {
  66                         config_file_eof = 1;
  67                         c = '\n';
  68                 }
  69         }
  70         return c;
  71 }
  72
  73 static char *parse_value(void)
  74 {
  75         static char value[1024];
  76         int quote = 0, comment = 0, space = 0;
  77         size_t len = 0;
  78
  79         for (;;) {
  80                 int c = get_next_char();
  81
  82                 if (len >= sizeof(value) - 1)
  83                         return NULL;
  84                 if (c == '\n') {
  85                         if (quote)
  86                                 return NULL;
  87                         value[len] = 0;
  88                         return value;
  89                 }
  90                 if (comment)
  91                         continue;
  92                 if (isspace(c) && !quote) {
  93                         space = 1;
  94                         continue;
  95                 }
  96                 if (!quote) {
  97                         if (c == ';' || c == '#') {
  98                                 comment = 1;
  99                                 continue;
 100                         }
 101                 }
 102                 if (space) {
 103                         if (len)
 104                                 value[len++] = ' ';
 105                         space = 0;
 106                 }
 107                 if (c == '\\') {
 108                         c = get_next_char();
 109                         switch (c) {
 110                         case '\n':
 111                                 continue;
 112                         case 't':
 113                                 c = '\t';
 114                                 break;
 115                         case 'b':
 116                                 c = '\b';
 117                                 break;
 118                         case 'n':
 119                                 c = '\n';
 120                                 break;
 121                         /* Some characters escape as themselves */
 122                         case '\\': case '"':
 123                                 break;
 124                         /* Reject unknown escape sequences */
 125                         default:
 126                                 return NULL;
 127                         }
 128                         value[len++] = c;
 129                         continue;
 130                 }
 131                 if (c == '"') {
 132                         quote = 1-quote;
 133                         continue;
 134                 }
 135                 value[len++] = c;
 136         }
 137 }
 138
 139 static inline int iskeychar(int c)
 140 {
 141         return isalnum(c) || c == '-' || c == '_';
 142 }
 143
 144 static int get_value(config_fn_t fn, void *data, char *name, unsigned int len)
 145 {
 146         int c;
 147         char *value;
 148
 149         /* Get the full name */
 150         for (;;) {
 151                 c = get_next_char();
 152                 if (config_file_eof)
 153                         break;
 154                 if (!iskeychar(c))
 155                         break;
 156                 name[len++] = c;
 157                 if (len >= MAXNAME)
 158                         return -1;
 159         }
 160         name[len] = 0;
 161         while (c == ' ' || c == '\t')
 162                 c = get_next_char();
 163
 164         value = NULL;
 165         if (c != '\n') {
 166                 if (c != '=')
 167                         return -1;
 168                 value = parse_value();
 169                 if (!value)
 170                         return -1;
 171         }
 172         return fn(name, value, data);
 173 }
 174
 175 static int get_extended_base_var(char *name, int baselen, int c)
 176 {
 177         do {
 178                 if (c == '\n')
 179                         return -1;
 180                 c = get_next_char();
 181         } while (isspace(c));
 182
 183         /* We require the format to be '[base "extension"]' */
 184         if (c != '"')
 185                 return -1;
 186         name[baselen++] = '.';
 187
 188         for (;;) {
 189                 int ch = get_next_char();
 190
 191                 if (ch == '\n')
 192                         return -1;
 193                 if (ch == '"')
 194                         break;
 195                 if (ch == '\\') {
 196                         ch = get_next_char();
 197                         if (ch == '\n')
 198                                 return -1;
 199                 }
 200                 name[baselen++] = ch;
 201                 if (baselen > MAXNAME / 2)
 202                         return -1;
 203         }
 204
 205         /* Final ']' */
 206         if (get_next_char() != ']')
 207                 return -1;
 208         return baselen;
 209 }
 210
 211 static int get_base_var(char *name)
 212 {
 213         int baselen = 0;
 214
 215         for (;;) {
 216                 int c = get_next_char();
 217                 if (config_file_eof)
 218                         return -1;
 219                 if (c == ']')
 220                         return baselen;
 221                 if (isspace(c))
 222                         return get_extended_base_var(name, baselen, c);
 223                 if (!iskeychar(c) && c != '.')
 224                         return -1;
 225                 if (baselen > MAXNAME / 2)
 226                         return -1;
 227                 name[baselen++] = tolower(c);
 228         }
 229 }
 230
 231 static int perf_parse_file(config_fn_t fn, void *data)
 232 {
 233         int comment = 0;
 234         int baselen = 0;
 235         static char var[MAXNAME];
 236
 237         /* U+FEFF Byte Order Mark in UTF8 */
 238         static const unsigned char *utf8_bom = (unsigned char *) "\xef\xbb\xbf";
 239         const unsigned char *bomptr = utf8_bom;
 240
 241         for (;;) {
 242                 int line, c = get_next_char();
 243
 244                 if (bomptr && *bomptr) {
 245                         /* We are at the file beginning; skip UTF8-encoded BOM
 246                          * if present. Sane editors won't put this in on their
 247                          * own, but e.g. Windows Notepad will do it happily. */
 248                         if ((unsigned char) c == *bomptr) {
 249                                 bomptr++;
 250                                 continue;
 251                         } else {
 252                                 /* Do not tolerate partial BOM. */
 253                                 if (bomptr != utf8_bom)
 254                                         break;
 255                                 /* No BOM at file beginning. Cool. */
 256                                 bomptr = NULL;
 257                         }
 258                 }
 259                 if (c == '\n') {
 260                         if (config_file_eof)
 261                                 return 0;
 262                         comment = 0;
 263                         continue;
 264                 }
 265                 if (comment || isspace(c))
 266                         continue;
 267                 if (c == '#' || c == ';') {
 268                         comment = 1;
 269                         continue;
 270                 }
 271                 if (c == '[') {
 272                         baselen = get_base_var(var);
 273                         if (baselen <= 0)
 274                                 break;
 275                         var[baselen++] = '.';
 276                         var[baselen] = 0;
 277                         continue;
 278                 }
 279                 if (!isalpha(c))
 280                         break;
 281                 var[baselen] = tolower(c);
 282
 283                 /*
 284                  * The get_value function might or might not reach the '\n',
 285                  * so saving the current line number for error reporting.
 286                  */
 287                 line = config_linenr;
 288                 if (get_value(fn, data, var, baselen+1) < 0) {
 289                         config_linenr = line;
 290                         break;
 291                 }
 292         }
 293         pr_err("bad config file line %d in %s\n", config_linenr, config_file_name);
 294         return -1;
 295 }
 296
 297 static int parse_unit_factor(const char *end, unsigned long *val)
 298 {
 299         if (!*end)
 300                 return 1;
 301         else if (!strcasecmp(end, "k")) {
 302                 *val *= 1024;
 303                 return 1;
 304         }
 305         else if (!strcasecmp(end, "m")) {
 306                 *val *= 1024 * 1024;
 307                 return 1;
 308         }
 309         else if (!strcasecmp(end, "g")) {
 310                 *val *= 1024 * 1024 * 1024;
 311                 return 1;
 312         }
 313         return 0;
 314 }
 315
 316 static int perf_parse_llong(const char *value, long long *ret)
 317 {
 318         if (value && *value) {
 319                 char *end;
 320                 long long val = strtoll(value, &end, 0);
 321                 unsigned long factor = 1;
 322
 323                 if (!parse_unit_factor(end, &factor))
 324                         return 0;
 325                 *ret = val * factor;
 326                 return 1;
 327         }
 328         return 0;
 329 }
 330
 331 static int perf_parse_long(const char *value, long *ret)
 332 {
 333         if (value && *value) {
 334                 char *end;
 335                 long val = strtol(value, &end, 0);
 336                 unsigned long factor = 1;
 337                 if (!parse_unit_factor(end, &factor))
 338                         return 0;
 339                 *ret = val * factor;
 340                 return 1;
 341         }
 342         return 0;
 343 }
 344
 345 static void bad_config(const char *name)
 346 {
 347         if (config_file_name)
 348                 pr_warning("bad config value for '%s' in %s, ignoring...\n", name, config_file_name);
 349         else
 350                 pr_warning("bad config value for '%s', ignoring...\n", name);
 351 }
 352
 353 int perf_config_u64(u64 *dest, const char *name, const char *value)
 354 {
 355         long long ret = 0;
 356
 357         if (!perf_parse_llong(value, &ret)) {
 358                 bad_config(name);
 359                 return -1;
 360         }
 361
 362         *dest = ret;
 363         return 0;
 364 }
 365
 366 int perf_config_int(int *dest, const char *name, const char *value)
 367 {
 368         long ret = 0;
 369         if (!perf_parse_long(value, &ret)) {
 370                 bad_config(name);
 371                 return -1;
 372         }
 373         *dest = ret;
 374         return 0;
 375 }
 376
 377 int perf_config_u8(u8 *dest, const char *name, const char *value)
 378 {
 379         long ret = 0;
 380
 381         if (!perf_parse_long(value, &ret)) {
 382                 bad_config(name);
 383                 return -1;
 384         }
 385         *dest = ret;
 386         return 0;
 387 }
 388
 389 static int perf_config_bool_or_int(const char *name, const char *value, int *is_bool)
 390 {
 391         int ret;
 392
 393         *is_bool = 1;
 394         if (!value)
 395                 return 1;
 396         if (!*value)
 397                 return 0;
 398         if (!strcasecmp(value, "true") || !strcasecmp(value, "yes") || !strcasecmp(value, "on"))
 399                 return 1;
 400         if (!strcasecmp(value, "false") || !strcasecmp(value, "no") || !strcasecmp(value, "off"))
 401                 return 0;
 402         *is_bool = 0;
 403         return perf_config_int(&ret, name, value) < 0 ? -1 : ret;
 404 }
 405
 406 int perf_config_bool(const char *name, const char *value)
 407 {
 408         int discard;
 409         return !!perf_config_bool_or_int(name, value, &discard);
 410 }
 411
 412 static const char *perf_config_dirname(const char *name, const char *value)
 413 {
 414         if (!name)
 415                 return NULL;
 416         return value;
 417 }
 418
 419 static int perf_buildid_config(const char *var, const char *value)
 420 {
 421         /* same dir for all commands */
 422         if (!strcmp(var, "buildid.dir")) {
 423                 const char *dir = perf_config_dirname(var, value);
 424
 425                 if (!dir) {
 426                         pr_err("Invalid buildid directory!\n");
 427                         return -1;
 428                 }
 429                 strncpy(buildid_dir, dir, MAXPATHLEN-1);
 430                 buildid_dir[MAXPATHLEN-1] = '\0';
 431         }
 432
 433         return 0;
 434 }
 435
 436 static int perf_default_core_config(const char *var __maybe_unused,
 437                                     const char *value __maybe_unused)
 438 {
 439         if (!strcmp(var, "core.proc-map-timeout"))
 440                 proc_map_timeout = strtoul(value, NULL, 10);
 441
 442         /* Add other config variables here. */
 443         return 0;
 444 }
 445
 446 static int perf_ui_config(const char *var, const char *value)
 447 {
 448         /* Add other config variables here. */
 449         if (!strcmp(var, "ui.show-headers"))
 450                 symbol_conf.show_hist_headers = perf_config_bool(var, value);
 451
 452         return 0;
 453 }
 454
 455 static int perf_stat_config(const char *var, const char *value)
 456 {
 457         if (!strcmp(var, "stat.big-num"))
 458                 perf_stat__set_big_num(perf_config_bool(var, value));
 459
 460         /* Add other config variables here. */
 461         return 0;
 462 }
 463
 464 int perf_default_config(const char *var, const char *value,
 465                         void *dummy __maybe_unused)
 466 {
 467         if (strstarts(var, "core."))
 468                 return perf_default_core_config(var, value);
 469
 470         if (strstarts(var, "hist."))
 471                 return perf_hist_config(var, value);
 472
 473         if (strstarts(var, "ui."))
 474                 return perf_ui_config(var, value);
 475
 476         if (strstarts(var, "call-graph."))
 477                 return perf_callchain_config(var, value);
 478
 479         if (strstarts(var, "llvm."))
 480                 return perf_llvm_config(var, value);
 481
 482         if (strstarts(var, "buildid."))
 483                 return perf_buildid_config(var, value);
 484
 485         if (strstarts(var, "stat."))
 486                 return perf_stat_config(var, value);
 487
 488         /* Add other config variables here. */
 489         return 0;
 490 }
 491
 492 int perf_config_from_file(config_fn_t fn, const char *filename, void *data)
 493 {
 494         int ret;
 495         FILE *f = fopen(filename, "r");
 496
 497         ret = -1;
 498         if (f) {
 499                 config_file = f;
 500                 config_file_name = filename;
 501                 config_linenr = 1;
 502                 config_file_eof = 0;
 503                 ret = perf_parse_file(fn, data);
 504                 fclose(f);
 505                 config_file_name = NULL;
 506         }
 507         return ret;
 508 }
 509
 510 const char *perf_etc_perfconfig(void)
 511 {
 512         static const char *system_wide;
 513         if (!system_wide)
 514                 system_wide = system_path(ETC_PERFCONFIG);
 515         return system_wide;
 516 }
 517
 518 static int perf_env_bool(const char *k, int def)
 519 {
 520         const char *v = getenv(k);
 521         return v ? perf_config_bool(k, v) : def;
 522 }
 523
 524 static int perf_config_system(void)
 525 {
 526         return !perf_env_bool("PERF_CONFIG_NOSYSTEM", 0);
 527 }
 528
 529 static int perf_config_global(void)
 530 {
 531         return !perf_env_bool("PERF_CONFIG_NOGLOBAL", 0);
 532 }
 533
 534 static struct perf_config_section *find_section(struct list_head *sections,
 535                                                 const char *section_name)
 536 {
 537         struct perf_config_section *section;
 538
 539         list_for_each_entry(section, sections, node)
 540                 if (!strcmp(section->name, section_name))
 541                         return section;
 542
 543         return NULL;
 544 }
 545
 546 static struct perf_config_item *find_config_item(const char *name,
 547                                                  struct perf_config_section *section)
 548 {
 549         struct perf_config_item *item;
 550
 551         list_for_each_entry(item, &section->items, node)
 552                 if (!strcmp(item->name, name))
 553                         return item;
 554
 555         return NULL;
 556 }
 557
 558 static struct perf_config_section *add_section(struct list_head *sections,
 559                                                const char *section_name)
 560 {
 561         struct perf_config_section *section = zalloc(sizeof(*section));
 562
 563         if (!section)
 564                 return NULL;
 565
 566         INIT_LIST_HEAD(&section->items);
 567         section->name = strdup(section_name);
 568         if (!section->name) {
 569                 pr_debug("%s: strdup failed\n", __func__);
 570                 free(section);
 571                 return NULL;
 572         }
 573
 574         list_add_tail(&section->node, sections);
 575         return section;
 576 }
 577
 578 static struct perf_config_item *add_config_item(struct perf_config_section *section,
 579                                                 const char *name)
 580 {
 581         struct perf_config_item *item = zalloc(sizeof(*item));
 582
 583         if (!item)
 584                 return NULL;
 585
 586         item->name = strdup(name);
 587         if (!item->name) {
 588                 pr_debug("%s: strdup failed\n", __func__);
 589                 free(item);
 590                 return NULL;
 591         }
 592
 593         list_add_tail(&item->node, &section->items);
 594         return item;
 595 }
 596
 597 static int set_value(struct perf_config_item *item, const char *value)
 598 {
 599         char *val = strdup(value);
 600
 601         if (!val)
 602                 return -1;
 603
 604         zfree(&item->value);
 605         item->value = val;
 606         return 0;
 607 }
 608
 609 static int collect_config(const char *var, const char *value,
 610                           void *perf_config_set)
 611 {
 612         int ret = -1;
 613         char *ptr, *key;
 614         char *section_name, *name;
 615         struct perf_config_section *section = NULL;
 616         struct perf_config_item *item = NULL;
 617         struct perf_config_set *set = perf_config_set;
 618         struct list_head *sections;
 619
 620         if (set == NULL)
 621                 return -1;
 622
 623         sections = &set->sections;
 624         key = ptr = strdup(var);
 625         if (!key) {
 626                 pr_debug("%s: strdup failed\n", __func__);
 627                 return -1;
 628         }
 629
 630         section_name = strsep(&ptr, ".");
 631         name = ptr;
 632         if (name == NULL || value == NULL)
 633                 goto out_free;
 634
 635         section = find_section(sections, section_name);
 636         if (!section) {
 637                 section = add_section(sections, section_name);
 638                 if (!section)
 639                         goto out_free;
 640         }
 641
 642         item = find_config_item(name, section);
 643         if (!item) {
 644                 item = add_config_item(section, name);
 645                 if (!item)
 646                         goto out_free;
 647         }
 648
 649         /* perf_config_set can contain both user and system config items.
 650          * So we should know where each value is from.
 651          * The classification would be needed when a particular config file
 652          * is overwrited by setting feature i.e. set_config().
 653          */
 654         if (strcmp(config_file_name, perf_etc_perfconfig()) == 0) {
 655                 section->from_system_config = true;
 656                 item->from_system_config = true;
 657         } else {
 658                 section->from_system_config = false;
 659                 item->from_system_config = false;
 660         }
 661
 662         ret = set_value(item, value);
 663
 664 out_free:
 665         free(key);
 666         return ret;
 667 }
 668
 669 int perf_config_set__collect(struct perf_config_set *set, const char *file_name,
 670                              const char *var, const char *value)
 671 {
 672         config_file_name = file_name;
 673         return collect_config(var, value, set);
 674 }
 675
 676 static int perf_config_set__init(struct perf_config_set *set)
 677 {
 678         int ret = -1;
 679         const char *home = NULL;
 680         char *user_config;
 681         struct stat st;
 682
 683         /* Setting $PERF_CONFIG makes perf read _only_ the given config file. */
 684         if (config_exclusive_filename)
 685                 return perf_config_from_file(collect_config, config_exclusive_filename, set);
 686         if (perf_config_system() && !access(perf_etc_perfconfig(), R_OK)) {
 687                 if (perf_config_from_file(collect_config, perf_etc_perfconfig(), set) < 0)
 688                         goto out;
 689         }
 690
 691         home = getenv("HOME");
 692
 693         /*
 694          * Skip reading user config if:
 695          *   - there is no place to read it from (HOME)
 696          *   - we are asked not to (PERF_CONFIG_NOGLOBAL=1)
 697          */
 698         if (!home || !*home || !perf_config_global())
 699                 return 0;
 700
 701         user_config = strdup(mkpath("%s/.perfconfig", home));
 702         if (user_config == NULL) {
 703                 pr_warning("Not enough memory to process %s/.perfconfig, ignoring it.", home);
 704                 goto out;
 705         }
 706
 707         if (stat(user_config, &st) < 0) {
 708                 if (errno == ENOENT)
 709                         ret = 0;
 710                 goto out_free;
 711         }
 712
 713         ret = 0;
 714
 715         if (st.st_uid && (st.st_uid != geteuid())) {
 716                 pr_warning("File %s not owned by current user or root, ignoring it.", user_config);
 717                 goto out_free;
 718         }
 719
 720         if (st.st_size)
 721                 ret = perf_config_from_file(collect_config, user_config, set);
 722
 723 out_free:
 724         free(user_config);
 725 out:
 726         return ret;
 727 }
 728
 729 struct perf_config_set *perf_config_set__new(void)
 730 {
 731         struct perf_config_set *set = zalloc(sizeof(*set));
 732
 733         if (set) {
 734                 INIT_LIST_HEAD(&set->sections);
 735                 perf_config_set__init(set);
 736         }
 737
 738         return set;
 739 }
 740
 741 static int perf_config__init(void)
 742 {
 743         if (config_set == NULL)
 744                 config_set = perf_config_set__new();
 745
 746         return config_set == NULL;
 747 }
 748
 749 int perf_config(config_fn_t fn, void *data)
 750 {
 751         int ret = 0;
 752         char key[BUFSIZ];
 753         struct perf_config_section *section;
 754         struct perf_config_item *item;
 755
 756         if (config_set == NULL && perf_config__init())
 757                 return -1;
 758
 759         perf_config_set__for_each_entry(config_set, section, item) {
 760                 char *value = item->value;
 761
 762                 if (value) {
 763                         scnprintf(key, sizeof(key), "%s.%s",
 764                                   section->name, item->name);
 765                         ret = fn(key, value, data);
 766                         if (ret < 0) {
 767                                 pr_err("Error: wrong config key-value pair %s=%s\n",
 768                                        key, value);
 769                                 /*
 770                                  * Can't be just a 'break', as perf_config_set__for_each_entry()
 771                                  * expands to two nested for() loops.
 772                                  */
 773                                 goto out;
 774                         }
 775                 }
 776         }
 777 out:
 778         return ret;
 779 }
 780
 781 void perf_config__exit(void)
 782 {
 783         perf_config_set__delete(config_set);
 784         config_set = NULL;
 785 }
 786
 787 void perf_config__refresh(void)
 788 {
 789         perf_config__exit();
 790         perf_config__init();
 791 }
 792
 793 static void perf_config_item__delete(struct perf_config_item *item)
 794 {
 795         zfree(&item->name);
 796         zfree(&item->value);
 797         free(item);
 798 }
 799
 800 static void perf_config_section__purge(struct perf_config_section *section)
 801 {
 802         struct perf_config_item *item, *tmp;
 803
 804         list_for_each_entry_safe(item, tmp, &section->items, node) {
 805                 list_del_init(&item->node);
 806                 perf_config_item__delete(item);
 807         }
 808 }
 809
 810 static void perf_config_section__delete(struct perf_config_section *section)
 811 {
 812         perf_config_section__purge(section);
 813         zfree(&section->name);
 814         free(section);
 815 }
 816
 817 static void perf_config_set__purge(struct perf_config_set *set)
 818 {
 819         struct perf_config_section *section, *tmp;
 820
 821         list_for_each_entry_safe(section, tmp, &set->sections, node) {
 822                 list_del_init(&section->node);
 823                 perf_config_section__delete(section);
 824         }
 825 }
 826
 827 void perf_config_set__delete(struct perf_config_set *set)
 828 {
 829         if (set == NULL)
 830                 return;
 831
 832         perf_config_set__purge(set);
 833         free(set);
 834 }
 835
 836 /*
 837  * Call this to report error for your variable that should not
 838  * get a boolean value (i.e. "[my] var" means "true").
 839  */
 840 int config_error_nonbool(const char *var)
 841 {
 842         pr_err("Missing value for '%s'", var);
 843         return -1;
 844 }
 845
 846 void set_buildid_dir(const char *dir)
 847 {
 848         if (dir)
 849                 scnprintf(buildid_dir, MAXPATHLEN, "%s", dir);
 850
 851         /* default to $HOME/.debug */
 852         if (buildid_dir[0] == '\0') {
 853                 char *home = getenv("HOME");
 854
 855                 if (home) {
 856                         snprintf(buildid_dir, MAXPATHLEN, "%s/%s",
 857                                  home, DEBUG_CACHE_DIR);
 858                 } else {
 859                         strncpy(buildid_dir, DEBUG_CACHE_DIR, MAXPATHLEN-1);
 860                 }
 861                 buildid_dir[MAXPATHLEN-1] = '\0';
 862         }
 863         /* for communicating with external commands */
 864         setenv("PERF_BUILDID_DIR", buildid_dir, 1);
 865 }